Species Biodiversity Action Plans (Summaries)

Species Biodiversity Action Plan - Dormouse

Common name: Common dormouse
Scientific name: Muscardinus avellanarius


The dormouse is a nocturnal, arboreal rodent that inhabits mixed broad-leaved woodland, hedgerows and orchards. Their main foods are flowers, pollen, seeds, nuts, berries and insects, particularly those amongst hazel, sweet chestnut and bramble.

During the day they sleep in a nest, often built in a hollow tree branch, deserted bird nest or a nestbox. Dormice are able to lower their body temperature and become torpid to save energy when food is scarce or poor weather prevents foraging; and in winter they hibernate from around October to April. Therefore, they spend around three quarter's of the year 'asleep'.

Dormice mainly occur in the south of the country (particularly Devon, Somerset, Sussex and Kent) with only a few recordings from north of the midlands (although they do exist in both the Lake District and Wales); and population densities tend to be low (less than 10 adults per hectare) even under favourable conditions. Female dormice usually only have one litter a year of between four young, although two litters can occur; with the breeding season and success rate being largely dependent on the weather.

Dormice generally have a head and body length of 60-90mm, a tail length of 57-68mm and a weight of 15-26g (10-15g for juveniles) increasing to 43g prior to hibernation.

Legal Protection

  • The dormouse appears in Appendix III of the Berne Convention (Convention on the Conservation of European Wildlife and Natural Habitats) which requires that they be protected from exploitation (indiscriminate mass killing, trading and any means capable of causing local disappearance or serious disturbance to them) and managed to keep them out of danger.
  • Dormice are also protected under Annex IV of the European Communities Council Directive on the Conservation of Natural Habitats and Wild Fauna and Flora, which covers species of community interest that are in need of strict protection. Damage or destruction of breeding sites or resting places is prohibited, and all life stages are protected against deliberate capture, killing or disturbance in the wild; and keeping, transport, sale/exchange and offering for sale/exchange of specimens.
  • Under domestic legislation, dormice are covered by the Wildlife and Countryside Act 1981 (as amended). Under Schedule 5 the deliberate killing, injuring, taking, possessing, disturbing and selling (including parts and derivatives) as well as damaging, destroying or obstructing any structure or place of refuge etc are prohibited. Under Schedule 6, certain methods of killing or taking animals are specifically prohibited, and even humane trapping for research requires a licence.
  • In addition the Conservation (Natural Habitats etc) Regulations 1994, states the requirement to conserve linear features in the countryside, and this is a feature of dormouse conservation.

Current Status

The dormouse does not occur in Scotland or Northern Ireland, and there are only a few known populations in Wales and Northern England. Indeed it has become extinct from up to 7 counties (or half its original range) over the last 100 years. In addition, although they are still widespread in southern England, populations are patchily distributed.

Internationally, the dormouse is widely distributed throughout central and eastern Europe; however, the UK holds around 25% of the world population.

Threats and Issues

  • Loss of broad-leaved ancient woodland - the ideal habitat for dormice (an area of at least 20ha is required to maintain a viable population).
  • Fragmentation of woodland - this leaves small, isolated populations that cease to be viable. Even distances as short as 100m are an absolute barrier to dispersal unless an arboreal route exists.
  • Hedge removal - causes both a direct loss of habitat and results in the increased isolation of woodland areas since hedges act as dispersal routes.
  • Changes in woodland management practices - particularly the cessation of long-rotation hazel coppicing, low diversity plantations and stock/deer incursion into woodland.
  • Grey squirrels - large populations of grey squirrels may reduce the availability of hazel nuts, and warfarin put out to control squirrel numbers may cause poisoning problems for dormice as well.
  • Climatic variations - these may impact on the breeding success of dormice.

Objectives (as pertinent to agriculture)

The national species action plan specifies two objectives:

  • To maintain and enhance dormouse populations in all the counties where they still occur.
  • To re-establish self-sustaining populations in at least 5 counties where they have been lost (Cambridgeshire, Nottinghamshire and three others yet to be determined).

Conservation Advice

  • Woodland management - the principle requirement is for a diverse habitat featuring a range of trees and shrubs capable of providing food throughout the summer. Good food sources are bramble (this should partially be cut back in the winter to ensure fresh growth and a good supply of fruit on two-year old growth) and honeysuckle (the bark is also used to build nests).
  • Coppice management - should be carried out on a long rotation (15-20 years) in order to ensure the productivity of nuts, and only very small areas of woodland (less than 0.5ha) should be cut each time, dotted throughout the wood.
  • Hedge planting - large species-rich hedgerows can be used to simultaneously link areas of woodland and provide additional habitat. Cutting should be done from one side at a time (the other side being cut 2-3 years later).
  • Rides - since dormice prefer not to travel across open ground, overhanging branches meeting across rides will provide them with an arboreal route.
  • Nest boxes - grants for erecting dormouse nest boxes (with the entrance facing a tree trunk) can be obtained under English Nature's Species Recovery Programme.

Species_dormouse_box.jpg (10914 bytes)

  • Poison hoppers - if these are to be used against grey squirrels, the advice of a pest control company should be sought to avoid the accidental poisoning of dormice.
  • Grant-aid incentives schemes - such as the Woodland Grant Scheme can be obtained to assist with suitable woodland management, and the Countryside Stewardship and Environmentally Sensitive Areas initiatives can be used   to fund hedge laying and restoration.
  • Re-introductions - this is often suggested, but it requires large areas of suitable woodland and long periods of supplementary feeding. In addition breeding animals in captivity is difficult and wild animals are unlikely to be available in sufficient quantities to be done on a large scale (at least 20 must be released into any new site).

References and Further Information

Andrews, J. and Rebane, M. (1994). Farming & Wildlife: A Practical Management Handbook. The Royal Society for the Protection of Birds, Sandy, UK.

Betts, C.J. (1998). Checklist of Protected British Species. Christopher Betts Environmental Biology, Worcester, UK.

Bright, P. & Morris, P.A. (1989). Occasional Publication No. 11: A Practical Guide to Dormouse Conservation. The Mammal Society, London.

Bright, P. and Morris, P. (1992). The Dormouse. The Mammal Society, London.

Bright, P., Morris, P. & Mitchell-Jones, T. (1996). The Dormouse Conservation Handbook. English Nature, Peterborough, UK.

Flowerdew, J.R. (1997). Mammal Biodiversity in Agricultural Habitats. In: Biodiversity and Conservation in Agriculture: Proceedings of a Symposium held at The Stakis Brighton Metropole Hotel 17 November 1997, (Ed. Kirkwood, R.C.), pp. 25-40. British Crop Protection Council, Farnham, UK.

The Mammal Society. (1997). Fact Sheet No. 1: The Dormouse Muscardinus arvellanarius. The Mammal Society, London.

UK Steering Group. (1995). Biodiversity: The UK Steering Group Report, Volume 2: Action Plans. HMSO, London.

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